Production of nitroalkanes

ABSTRACT

A process for the production of a nitroalkane or dinitroalkane by reacting an olefin or diolefin with nitric acid in the presence of a lower aliphatic monocarboxylic acid anhydride, thereby producing a nitro-ester or dinitro-ester, and reducing the nitro-ester or dinitro-ester with an alkali borohydride to produce the nitroalkane or dinitroalkane.

United States Patent Bachman et al.

[451 Dec. 19,1972

[541 PRODUCTION OF NITROALKANES [72] inventors: Gustave Bryant Bachman,Lafayette; Stephen E. Eisenstein, West Lafayette, both of Ind.

[73] Assignee: Purdue Research Foundation [22] Filed: Oct. 18, 1971 [21]Appl. No.: 190,403

[52] US. Cl. ..260/644, 260/466, 260/467 [51] int; Cl. ..co7 79/04 C 07c7 9 /08 [58] Field of Search .260/466, 467,644

[56] References Cited UNITED STATES PATENTS Wekeil et al. ..260/4673,510,531 5/1970 Larkin et al. ..260/644 3,658,922 4/1972 Drake..260/644 FOREIGN PATENTS OR APPLICATIONS 476,873 9/1951 Canada..260/644 Primary Examiner-Leland A. Sebastian Attorneyi-ioward E. Postet al.

[57] ABSTRACT 5 Claims, No Drawings PRODUCTION OF NITROALKANFS SUMMARYOF THE INVENTION to produce nitroalkyl acetates and nitrates, along withnitroalkenes (acetyl nitrate must be handled with caution; violentdecomposition may occur at 6070C to dinitrogen pentoxide and loweroxides but it is reasonably stable at lower temperatures, especiallywhen in dilute solution). It is also known from A. I. Meyers and J. C.Sircar, J. Org. Chem. 32, 4134 1967) to reduce nitroalkenes tonitroalkanes with sodium borohydride.

Nitroalkanes are produced commercially by the vapor phase nitration ofpropane, which yields useful quantities of the four lower nitroalkanesplus very small amounts of land Z-nitrobutanes. The nitration of alkanesof higher molecular weight than propane is impractical because themultiplicity of products makes separation and purification prohibitivein cost. A need exists therefore for a process whereby a nitroalkane canbe produced selectively.

SUMMARY OF THE INVENTION It is an object of this invention to provide aprocess for the production of nitroalkanes.

It is another object of this invention to provide a process forselectively producing a nitroalkane from an olefin.

It is still another object of this invention to provide a process forthe selectively producing a dinitro-alkane from a diolefin.

Other objects of this invention will be apparent to those skilled in theart from the disclosure herein.

It is the discovery of the present invention to provide a process forproducing a selected nitroalkane from a selected olefin or a selecteddinitroalkane from a selected diolefin. According to the presentinvention, the selected olefin, or diolefin, is reacted with nitric acidin the presence of a lower aliphatic carboxylic acid anhydride therebyconverting the olefin or diolefin to the corresponding nitroalkanolester or dinitroalkanediol diester. The product so obtained is reactedwith sodium borohydride thereby producing the nitroalkane ordinitroalkane. The process is particularly advantageous in that nosubstantial concentration of nitroolefin is produced and it is carriedout in a single reaction vessel without isolation of intermediates,thereby minimizing operating costs and preventing reduced yield throughloss of product. Furthermore, excess acid anhydride is not needed as asolvent, temperatures below those obtainable with an ice bath are notneeded, and large concentrations of explosive acetyl nitrate are neverpresent.

DETAILED DISCUSSION Olefins and diolefins useful in the presentinvention correspond to the formula where R and R can be hydrogen oralkyl, e.g., alkyl of one to three carbon atoms, and can be the same ordifferent; R is alkyl of one to six carbon atoms or R can be the group(R CH=CH)-; or R and R taken together can be an alkylene group, e.g.,butylene, thereby forming a cyclohexene ring.

The nitroalkanes and dinitroalkanes therefrom correspond to the formulaobtained R N0, R3([JH(J3HR wherein R and R have the same meaning definedabove and R is an alkyl group of one to six carbon atoms or the group orR and R taken together can collectively be a butylene group forming acyclohexane ring.

The reaction is carried out in a vessel equipped with an agitationmeans, a temperature indicator, a cooling means, and an inlet means. Theolefin is mixed with acid anhydride, e.g., acetic anhydride, in a ratioof about 1 to 24 moles of said anhydride (in a l to 4-8 moles ratio ifthe olefin is a diolefin). If the olefin is a lolefin, i.e. when R ishydrogen, concentrated sulfuric acid is preferably, but not necessarily,added at this point in a mole ratio of about 0.0 l0.02:1 of the olefinto catalyze the reaction. The sulfuric acid should not be used withcyclohexene because the temperature is virtually uncontrollable in thepresence of sulfuric acid. Nitric acid, about 1.5 moles per mole ofolefin or 3 moles per mole of diolefin, preferably but not necessarily,an aqueous solution containing about percent by weight I-INO is thenadded gradually with agitation, maintaining the temperature at, e.g.,about 25 C. Generally the mixture is agitated for a time sufficient toinsure substantial completeness of reaction, e.g. from l-hours, therebyforming the nitro-ester.

To the solution is then gradually added sodium hydroxide in a mole ratioof about 0.9 mole per mole of acetic anhydride. Preferably the sodiumhydroxide is in the form of a solution, e.g., an aqueous solution.Preferably the temperature of the reaction mixture is controlled toabout 20 or below. To the resulting mixture is then added sodiumborohydride in a mole ratio of about 1 mole per mole of olefin or 2moles per mole of diolefin, dissolved in a suitable solvent, e.g.,dimethylsulfoxide (hereafter designed DMSO), maintaining the temperaturegenerally at about 2025C.

Generally the mixture is agitated for a time to allow the reaction to goto completion, e.g., for about 30 min., and is then diluted with about 2volumes of cold water and the product is extracted with ether. It isthen recovered by any suitable means, e.g., by evaporation of the etherand steam distillation or vacuum distillation of the residue.

Olefins and diolefins useful for the practice of this invention arethose corresponding to the foregoing general formula, i.e., those havingfrom one to three active hydrogen atoms on the carbon atoms of thedouble bonds. Ethylene is inoperable because the addition of acylnitrate does not occur. The ease of addition of the nitro groupincreases with the degree of substitution on the unsaturated carbonatoms, but the tetra-substituted olefins are inoperable because theaddition compound cannot be reduced to nitro-alkane, i.e., no activehydrogen atoms are present. The ease of reduction of the additionproduct increases with decreasing degree of substitution. Typicalolefins and diolefins preferred for the practice of this inventioninclude but are not limited to l-butene, l-octene,3,3-dimethyl-1-butene, cyclohexene, 2-butene, Z-methyl-l-butene,2-methyl- 2-butene, 1,3-butadiene and 2-methyl-2,4-pentadiene. Manyother suitable olefins and diolefins are known.

The practice of the invention is not limited to the use of aceticanhydride, but inasmuch as the acid. anhydride is consumed in thereaction and does not form a part of the product, it is generallyimpractical and uneconomical to employ others. The ordinary commercialgrade acetic anhydride is suitable. Propionic anhydride has also beenused with equivalent results, and butyric anhydride is similarlysuitable.

Sodium borohydride is known in the art and is commercially available.The ordinary grade of commerce is suitable for the practice of thisinvention.

The invention will be better understood with reference to the followingexamples. It is understood however that these examples are intended forillustration only and it is not intended that the invention be limitedthereby.

EXAMPLE 1 In a 250 ml three-necked flask was placed 25.0 ml (0.265 mole)of acetic anhydride and 15.6 ml (0.10 mole) of l-octene. The mixture wascooled to and 6.6 ml (0.1 mole) of 70 percent'nitric acid was addeddropwise. The reaction mixture was allowed to warm to room temperatureand stirred for 4 hrs. The adduct was reduced in situ with 6.10 g (0.15mole) of sodium borohydride in 130 ml DMSO, and bromobenzene was addedas internal vapor phase chromatography (vpc) standard. The reactionmixture was stirred 1 hr and poured into ice water. The aqueous solutionwas extracted with 3 X ml ether. Analysis via vpc showed a 34 percentconversion (46 percent yield) to l-n'itrooctane.

EXAMPLE 2 no unreacted acetic anhydride but a trace of l-octene.

Analysis at 4 hr showed only a slight decrease in the amount ofI-octene. The reduction was carried out at this point with 3.53 g (0.091mole) of sodium borohydride in 75 ml of DMSO. Due to severe foaming,

a few drops of Dow-Corning Antifoam Q were added X 25 ml of ether.Bromobenzene was added to the ether layer as an internal vpc standard.Analysis by vpc showed a 53 percent conversion (58 percent yield) of 1-nitrooctane.

EXAMPLE 3 Z-Methyl-l-butene, 21.4 g (0.3 mole), and 113 ml (1.2 mole) ofacetic anhydride were placed in a 500 ml Morton flask, and 1 ml ofsulfuric acid was added. Nitric acid (0.45 mole) was added through apressure equalizing dropping funnel while maintaining the temperaturebetween 20-30 with an ice-water bath. The solution was stirredovernight, and a solution of 42 g (1.05 mole) of sodium hydroxide in 40ml of water was added, while keeping the temperature below 20. To thisslurry was added 11.50 g (0.29 mole) of sodium borohydride in 210 ml ofDMSO while keeping the temperature 20-25. The reaction mixture wasstirred for 1 hr, quenched in water and extracted with ether. There wasobtained 1-nitro-2-methylbutane.

EXAMPLE 4 A four-necked flask was charged with 32 ml (0.3 mole) of2-methyl-2-butene, and 113 ml (1.2 mole) of acetic anhydride. Nitricacid (30 ml, 0.45 mole) was added from a non-pressure equalizingdropping funnel while keeping the temperature at 20-30; a condenser wasused to prevent loss of the low boiling olefin. The solution was stirreduntil the exothermic phase was complete. To this solution was added 42 g(1.05 mole) sodium hydroxide in 45 ml of water while keeping thetemperature below 20. The resulting thick slurry was stirred for 0.5 hrand 11.84 g (0.30 g (0.30 mole) of sodium borohydride in 225 m1 DMSOadded at 2025 The mixture was stirred for 1 hr and quenched in coldwater. The aqueous mixture was extracted with 3 X 5 ml of ether.

Distillation gave 2-nitro-3-methylbutane, bp 58 (18 mm).

EXAMPLE 5 The foregoing experiment was repeated in all essential detailsexcept that the reduction step was effected at 60. The addition wentsmoothly withno apparent reaction. After about 5-10 min some bubblingwas noted and the reaction became vigorous, a stable foam formed and 5ml DMSO were added to wash it down. The reaction mixture was stirred 1.5hr, quenched in water and the product extracted with ether. Thenitroalkane was then distilled, bp 58 17 mm).

EXAMPLE 6 Nitric acid, 30 ml (0.45 mole), was added dropwise to 113 ml(1.2 mole) of acetic anhydride, and 30.5 ml (0.3 mole) of cyclohexene.The temperature was easily controlled at 2030. The reaction was quenchedin 600 ml of ice water, ml of ether and 5 g urea were added. Afterextraction with ether, the ether layer was dried over magnesium sulfate.The ether was evaporated and the residue reduced with 11.34 g (0.29mole) of sodium borohydride in 250 ml of DMSO. After stirring thereduction mixture for 1 hr, it was quenched in water and extracted withether. The product was steam distilled, extracted with ether, dried,

concentrated and vacuum distilled through a 13 cm Vigreux column. A goodyield of nitrocyclohexane was obtained.

EXAMPLE 7 The experiment of Example 2 was repeated in all essentialdetails except that l-butene was substituted for l-octene on anequi-molar basis. There was obtained 1- nitrobutane in good yield.

EXAMPLE 8 The experiment of Example 7 was repeated in all essentialdetails except that 2-butene was substituted for l-butene. There wasobtained 2-nitrobutane in good yield.

EXAMPLE 9 The experiment of Example 2 was repeated in all essentialdetails except that 3,3-dimethyl-l-butene was substituted for l-octeneon an equi-molar basis. There was obtained, 3,3-dimethyl-l-nitrobutane.

EXAMPLE 10 where R and R are hydrogen or alkyl of one to three carbonatoms and R is alkyl of one to six carbon atoms or the group or R and Rtaken together are collectively a butylene group, comprising the stepsof a. mixing an olefin or diolefin corresponding to the formula where Rand R have the same meaning as hereinbefore defined and R is alkyl orthe group (RCH=CH), or R and R taken together are a butylene group, witha lower aliphatic carboxylic acid anhydride, said olefin being in aratio of about 1 mole to 2-4 moles of said anhydride or about 1 mole ofsaid diolefin to about 4-8 moles of said anhydride,

b. adding nitric acid thereto at a ratio of about 1.5 moles per mole ofsaid olefin, or 3 moles per mole of said diolefin, while maintaining thetemperature at about 25C,

c. agitating for a length of time sufficient to substantially convertsaid olefin or diolefin to the corresponding nitro-alkanol ester ordinitroalkanediol diester, d. adding sodium hydroxide in a ratio ofabout 0.9

moles per mole of said anhydride while maintaining the temperature atabout 20C, adding sodium borohydride in a mole ratio of about 1:1 ofsaid olefin or about 2:1 of said diolefin while maintaining thetemperature at about 20-25C, and agitating for about 30 min,

e. adding the mixture thereby obtained to about 2 volumes of cold water,

f. and recovering said nitroalkane or dinitroalkane therefrom.

2. The process of claim 1 wherein said olefin is a diolefin.

3. The process of claim 1 wherein said acid anhydride is aceticanhydride.

4. The process of claim 1 wherein said olefin is a lolefin and step (b)is effected in the presence of sulfuric acid, 0.01-0.02 moles per moleof said olefin.

5. The process of claim 1 wherein said nitric acid is an aqueoussolution containing HNO .TJNTTTD STATES PATENT QTTTQT @ERTEMCATE @F QO-REQ'N ON Paten 7., 7.064808 Dated, Degggbe'r Q..,,.,.l-9,7,,2

It is certified that appears in the above iflefifi fid patent and thatsaid Letters 'Iatent are hereby lzricted as shwn B'QlfiW? Signed andsealed this 10th day of July (SEAL) Attest:

EDWARD M.PLETCHER,JR.

Rene Tegtmejyer Attestlngofflcer Acting Clommiss ivner 0f Patents FORMPo wso (10-69) UNITED STATES FATENT @FFICE '(IERTIFEQA'EE 6F Q ORRECTIGNPatent N ,706,808 0 H Da fl..v,Dece rg b,ef L9,.W1972 inventors) pGustaveflllchman.andmfitephen ufiilfis nsjcwein.

It is certified that fii appears in the 'abOV-ifififiifid patent andthat said Letters Patent are hereby corrected as ihm Malawi Cblumn 2,line 49 "1-" should be =-1-'4* Signed and Sealed this 10th day of July1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer Rene Tegtmeiyr I 1 ActingCommissioner of Patents F ORM PO-1050 (10-69)

2. The process of claim 1 wherein said olefin is a diolefin.
 3. Theprocess of claim 1 wherein said acid anhydride is acetic anhydride. 4.The process of claim 1 wherein said olefin is a 1-olefin and step (b) iseffected in the presence of sulfuric acid, 0.01-0.02 moles per mole ofsaid olefin.
 5. The process of claim 1 wherein said nitric acid is anaqueous solution containing 70% HNO3.